Retort ovens have been known for a long time such as, for example, as is disclosed in DE-0S 198 44 136. In retort ovens of this type, a wax model of a dental restoration is embedded in a cast bed in order to produce a negative form. The retort is then heated and warmed so that the model composed of wax melts and there remains the temperature resistant negative form or mold in readiness for the introduction thereinto of a to-be-pressed ceramic mass.
Dental restoration can demand decidedly different forms and volumes. Correspondingly, at the same time several wax models are frequently made ready in a single batch—that is, several wax models are poured within a single retort—and, correspondingly, several ceramic restoration pieces are produced via pressing. The pressing is performed with ceramic mass which is introduced via a feed-in channel and formed into the form mass by a press stamp during simultaneous heating of the negative form.
The mass can be introduced in a pre-pressed condition, in a powder-type condition, or even in a fluid condition, whereby the pre-pressed form body is typically designated as a blank.
Instead of blanks, powder-formed ceramic masses can also be deployed. The use of blanks has, on the one hand, the advantage that an exact or precisely measured amount of ceramic material is deployed so that the operation of the stamp for exerting pressure in the press oven can be exactly specified and can be corrected with a corresponding material offset.
The dental restoration component to be produced can require significantly different amounts of ceramic—either in the form of ceramic powder or in the form of ceramic blanks.
In order to competently handle these requirements, the length of the ceramic blank can be adapted to the requirements, within certain limits. The ceramic blank is introduced into the channel which remains as the negative form of the retort cylinder. In order to achieve a press result of high quality, the ceramic blank must practically be comprised of the same diameter as that of the retort cylinder.
One can, indeed, increase the length of the retort cylinder and, consequently, increase the possible length of the ceramic blank. However, in connection with an overly long length, there arises a comparatively large friction during the press process. This is unfavorable from, for example, the perspective of the adhesion/sliding friction conditions during the press process, which have only been studied to a limited degree and in connection with which there occur pressure oscillations in the hollow space in which the dental restoration is configured.
In order to competently handle various sizes of dental restorations, it has heretofore typically been the practice to maintain a plurality of different retort cylinders in readiness so that, in connection with larger dental restorations of large diameter, larger diameter versions of the retort cylinder can be deployed.
However, maintaining in readiness an inventory of several retort systems of various sizes is a relatively large effort, simply from the point of view of requiring a correspondingly large inventory.
In order to avoid this, it has frequently been the case that an average-sized configuration of a retort system or a retort arrangement is deployed and then several restoration components are stuck outwardly from wax on the growth surface via corresponding support arms, so that the mass is, in total, somewhat enlarged and the blank can be better exploited.
However, imperfect accommodation to the required dental restoration configurations leads to considerable material loss, since, in the case of an only partially pressed blank, the blank must, for all practical purposes, be thrown away.
If, on the other hand, in connection with a desired large material mass, a blank of an overly long length is deployed such that it extends out of the channel of the corresponding retort cylinder, the danger exists that the blank will tip, leading to an unstable press process.